The human interleukin-2 (IL2R) is being studied in order to understand specific critical components of the T cell immune response in normal and neoplastic cells. The approaches used are based on (1) biochemical analysis of high and low affinity IL2R; (2) identification of key transcriptional regulatory sequences in the IL2R gene; (3) identification of DNA binding proteins for regulatory regions: (4) analysis of the importance of post- transcriptional regulation for IL2R gene expression. We have identified a 65 to 77 kD glycoprotein component of the high affinity human IL2R, distinct from Tac antigen. This protein, denoted p70 or the IL2R beta chain, is itself an IL2 receptor, independent of its association with Tac antigen. We have demonstrated that p70 appears to mediate both the generation of lymphokine activated killer cell and IL2R-induced augmentation of natural killer cell activity. It is present on resting CD4 and CD8 positive T cells, and can be induced on B cells and monocytes. Using IL2R cDNA and genomic constructs, we have partially mapped the region of the IL2R gene necessary for transcriptional activity. We have identified: (1) a region functioning as an IL2R negative regulatory region in HTLV-I transformed T cell lines; (2) a requirement for a larger promoter region in Jurkat cells than in HTLV-I transformed T cells: (3) the ability to utilized a smaller promoter in Jurkat cells, analogous to Htlv-I transformed T cells, by cotransfection with tat-I; (4) several regions of DNA that putatively bind proteins based on exonuclease assays and band shift experiments. We have also identified a new gene, Act2, absent in resting T cells but induced with 30 minutes of exposure to PHA, reaching maximal levels by 4 hours and then significantly falling by 16 hours.